When a metal object is dropped into cold water, it releases 4,715 J of energy to its surroundings, and its temperature decreases from [y].0 °C to 20.0 °C. The mass of the object is [x] grams. What is the specific heat of this material?

For the reaction Cl2 + 2 Br- → 2 Cl- + Br2, which of the following statements is NOT correct?

What volume in L of a 0.32 M Mg(NO3)2 solution contains [x] g of Mg(NO3)2 ? The molar mass of Mg(NO3)2 is 148.33 g/mol

What is the coefficient in front of the O2 when the equation below is balanced (using only whole numbers and the lowest whole number ratio)? C2H4(g) + O2 (g) → CO2(g) + H2O (g)

What is the mass, in grams, of [x] × 1021 silicon atoms?

Which picture BEST represents a mixture?  

Consider the following reaction: Mg2+(aq) + Cu(s) → Cu2+(aq) + Mg(s). In this reaction, Mg2+(aq) is:

Consider the Haber-Bosch process for the synthesis of ammonia from its elements. Calculate the theoretical yield in moles NH3 from the complete reaction of [x] grams N2 in the presence of excess H2 gas according to the following balanced chemical equation: N2(g) + 3 H2(g) → 2 NH3(g)

A chemist carries out this reaction in the laboratory using 4.31 grams of zinc and an excess of sulfur:    Zn + S → ZnS From the balanced equation, she calculates that she should obtain 6.41 grams of zinc sulfide. However, she isolates only [x] grams of product. What is her percent yield for this reaction?

In this Lewis structure, which atom does not have a complete valence?